If someone owns a piece of property and allows unabated trespassing across the property for long periods of time, and then arbitrarily starts enforcing their property rights, real estate law tells them they may not have the rights to do this, even if they own the property. Currently, we have a new type of trespassing that is absolutely out of control - Foreclosure Squatting.
This is where someone, could even be a homeless person moves into an empty property and just starts living there. After the subprime lending debacle the number of foreclosed homes has risen by nearly 3500%. With all these home vacated, it is prime pickings for someone moving in. Worse, many of the banks that own these properties have let them go, and have not even been out to see if anyone has moved in illegally.
Even if they do inspect the property, getting a squatter to leave is not as easy as it seems. Now many enforcement agencies will not even serve foreclosure demands to remove people from a property. Worse, the note holders who've bought the mortgages and own the homes may not even be in the United States.
If a foreclosed empty home becomes a de facto residence for the homeless, a habitat for wildlife, an alternative parking lot for the neighborhood, a short-cut to the next block or community center for the locals, then once it's sold these groups could indeed sue to maintain their new rights. Especially after many years of unabated activity in the empty homes. Think on this.